1. Field of the Invention
The present invention relates to a control apparatus, a control method, and a non-transitory computer readable medium storing a control program. In particular, the present invention relates to a control apparatus, a control method, and a non-transitory computer readable medium storing a control program for a DC (Direct Current) motor.
2. Description of Related Art
These days, shape measuring means such as a three-dimensional measuring device (hereinafter, also referred to as a “3D measuring device) is used to inspect the machining accuracy (or processing accuracy) of a product having a 3D (three-dimensional) shape. Such shape measuring means carries out shape measurement, for example, by moving a probe along a 3D shape.
As shown in FIG. 9, Japanese Unexamined Patent Application Publication No. 2013-21804 discloses a control technique for performing feedback control for a drive motor of shape measuring means by using triple control loops including a position, a speed and a current.
The control technique disclosed in Japanese Unexamined Patent Application Publication No. 2013-21804 requires, for example, using a current detection sensor capable of measuring a large current value. The accuracy of a current detection sensor has a linear relation with its maximum detection value. Therefore, a sensor capable of measuring a large current value has poor detection accuracy for small current values. Therefore, when a drive motor that requires a large current is controlled, there is a problem that the control performance deteriorates in the range of small currents.